1. Field of Invention
This invention relates to rotatable handle grips that improve the performance of a broad range of items including tennis racquets, hockey sticks, kayak oars, and rotary hand tools.
2. Description of Prior Art
Although this invention can be applied to many items, only two types of items, tennis racquets and screwdrivers, will be discussed in detail since they represent a broad range of possible applications.
In the game of tennis a racquet is usually rotated to different positions relative to a players hand when preparing for backhand, forehand or volley shots. Most players utilize more than one grip position for each of those shots. For example, when hitting a backhand shot the player can impart either slice (underspin) or topspin (overspin) to the ball, but each shot can be performed more efficaciously using different grip positions.
Different grip positions determine the degree of angular racquet head displacement relative to a player""s hand This determines the angle of the racquet face relative to the ground at the moment of impact with a tennis ball during a tennis stroke. A topspin shot would require a slightly acute angle, while a slice shot would require a somewhat obtuse angle. This rotational displacement can be controlled by a rotatable handle grip that can provide a player with increased accuracy, control, power, consistency, hand comfort and decreased response time. However, rotatable handle grips that can be locked in only a limited number of predetermined positions, or that cannot be adjusted easily and instantaneously during play, are inefficacious because they limit not only the types of shots a player can make but the quality of play in general.
Rotatable handle grips also improve the performance of many hand tools that require rotation, such as screwdrivers. Such rotatable handle grips usually operate with a ratcheting mechanism, allowing the handle grip to rotate freely about the shaft of a tool in only one direction at a time. When the user rotates the handle grip in the opposite direction, the tool rotates with the handle grip. If a user wishes to rotate the tool in the opposite direction, he must slide or twist a setting switch prior to use, a time consuming and bothersome procedure. Manufacture and assembly of the numerous moving parts is relatively complex, resulting in production costs far above that of conventional stationary handle grip screwdrivers.
Previous rotatable handle grips suffered from the above-mentioned problems as well as these discussed below.
U.S. Pat. No. 2,019,512 to Marsh (1936) discloses a golf club handle which had to be xe2x80x9csetxe2x80x9d in position. This involved a cumbersome and time-consuming process; a user was required to loosen a nut at the base of the handle, disengage a toothed mechanism, estimate where the desired setting might be, reengage the teeth, and finally retightening the base nut Consequently, this handle grip mechanism could not provide any benefit if applied to a tennis racquet since the user would be unable to rotate the handle grip to different positions during play.
Marsh""s handle could not provide a ratcheting effect, or selectively transfer torque, thereby making it equally non-beneficial for screwdrivers.
U.S. Pat. No. 4,693,475 to Keilhau (1987) shows a tennis racquet similar to Marsh""s. In Keilhau""s, however, the clutch comprises an acutely angled conical component on the handle shaft, and a corresponding funnel shape on the handle grip. Keilhau""s handle grip was an improvement over Marsh""s handle grip in that it could be set in an infinite number of positions because it possessed no teeth; nonetheless, it provided no means for rotating the handle grip to different positions during play.
German patent DE 35 10598 A1 to Pankonin (1986) shows a handle grip similar to Keilhau""s, but Pankonin""s provides a powerful tension spring rather than a locking nut, and less acutely angled clutch surfaces. Unfortunately, the spring tension required to prevent axial rotation of the racquet during off-center shots was enormous; this made quick handle grip position changes during play nearly impossible.
In U.S. Pat. No. 3,534,960 to Hanks (1970), a rotatable tennis racquet handle grip was proposed which could be locked in only three predetermined positions. Hanks"" handle grip was also complicated to operate. The user was required to perform three precisely timed sequential operations in order to change from one grip setting to another. First a spring loaded dog-pin mechanism had to be xe2x80x9cunlockedxe2x80x9d by depressing a thumb tab. Next the user rotated the grip about the handle. The user then had to release the thumb tab at precisely the correct spot to situate the dog-pin into one of three hole settings. Since the handle grip was normally in a locked position, if the user applied rotational force to the handle grip prior to depressing the thumb tab, the mechanism could jam; even worse, the dog-pin or opposing parts could shear or bend. Likewise, if the user did not release the thumb tab at, or immediately prior to the desired hole setting while rotating the handle grip, it could lock in the wrong position, or not even lock at all.
The preferred Hanks"" embodiment, containing only three settings, created an inflexible system. The rotational displacement between each setting was overly large; very small changes in angular displacement are needed. Without such control the racquet-face will not be at the correct angle relative to the ground at the moment of impact with a ball during a tennis stroke. Adding more holes would have confused the user; there was no way to quickly and easily distinguish among even the few settings which were provided. Too many holes would have also greatly increased the chance of part failure due to shear; the greater the number of holes, the smaller each hole would need to be to remain separated, and the thinner the dog-pin would need to be.
Finally, Hanks"" mechanism did not address the extremely important factor of user compatibility. The user was forced to delicately place his thumb on a tab longitudinally along the handle grip. The thumb had to remain there for much of the time during play in order to be prepared for quick changes of grip positions. When gripping the handle in such an awkward and unnatural manner, it is extremely difficult to maintain a firm grip and control of the racquet when hitting a tennis ball. Furthermore, a player could inadvertently unlock the handle grip from its setting; there is a natural tendency to squeeze the handle grip of a tennis racquet more firmly at the moment the racquet impacts the ball. If the mechanism for changing grip positions is cumbersome, time consuming, unreliable, and distracting to use, it is not appropriate for use in a game which requires intense concentration and nearly instantaneous grip changes.
Hanks"" tennis racquet handle grip mechanism was also inappropriate for performing a ratcheting effect on screwdrivers.
In U.S. Pat. No. 4,101,125 to Heath (1988) a rotatable tennis racquet handle grip was proposed. It employed a spring loaded grip-sleeve with a peg and grove locking mechanism. The handle grip had only two settingsxe2x80x94forehand and backhand As mentioned earlier, a handle grip that provides only a limited number of predetermined positions is inefficacious.
Adding many positions would not be possible; the mechanism necessitates a large rotational displacement between positions in order to prevent part failure due to shear. Furthermore, the user would be unable to easily and quickly distinguish between positions, and accurately reengage the locking peg in a desired slot.
The mechanism increased response time during play and was also susceptible to jamming. The user was required to xe2x80x9cunlockxe2x80x9d the handle grip by moving it longitudinally up the racquet shaft prior to rotating the handle grip to a new position. This extra motion increased the amount of time needed to change from one grip position to another. In many circumstances during play, the grip change could not be performed in time to hit the ball. If the player, in his haste, attempted to rotate the handle grip prior to xe2x80x9cunlockingxe2x80x9d it, the mechanism could jam.
The handle grip relied on a spin to keep it xe2x80x9clockedxe2x80x9d in position during play. As a consequence, the user experienced uncomfortable vibration from the handle grip when hitting a tennis ball.
Still another barrier to the use of Heath""s grip was the extreme awkwardness and discomfort it presented to players who use a xe2x80x9ctwo-handed gripxe2x80x9d. In order to change grip positions with Heath""s handle grip, such players were required to remove one of their hands from the grip, and place it on the racquet shaft, move the handle grip longitudinally up the shaft of the racquet, and regrasp the handle grip with both hands. Such a process is cumbersome and time consuming.
As with other racquet handle grips, Heath""s handle grip was also inappropriate for performing a ratcheting effect on screwdrivers.
U.S. Pat. No. 4,365,807 to Melby (1982) shows a golf club with rotatable handle which could be adjusted during use. To operate the handle, a user was required to first xe2x80x9cunlockxe2x80x9d the grip. That was accomplished by moving the handle grip longitudinally up the golf club shaft, thereby disengaging a spring-loaded toothed locking system. The user then rotated the handle grip relative to the golf club, and allowed the spring to reengage the mechanism in the desired position. As with Heath""s handle grip, this method was both time consuming and cumbersome because it forced the user to effectuate both longitudinal and rotational movement to change settings. Additionally, the nature of the tooth mechanism with its finite number of teeth necessitated a large racquet head angular displacement between each setting which, as mentioned previously, is not practicable for racquet applications. This grip mechanism also suffered from vibration during use, primarily caused by the spring.
In the form presented, Melby""s handle grip would be ineffective for producing a ratcheting effect on screwdrivers. If the spring action was reversed, a ratcheting effect could be accomplished. Such a mechanism, however, was already described in U.S. Pat. No. 2,712,765 to Knight (1955), discussed below.
U.S. Pat. No. 4,854,596 to Carbonetti (1989) shows a tennis racquet with an angularly adjustable handle grip. Carbonetti combined the mechanisms of Melby""s and Heath""s handle grips, but reversed the direction of both the spring action and engagement of the locking mechanism. Consequently, Carbonetti""s handle grip experienced the same limitations found in the handle grips of Melby and Heath. Moreover, the handle grip was more difficult to use; it needed a powerful spring to prevent partial disengagement of the locking mechanism due to centripetal force incurred during a stroke.
U.S. Pat. No. 4,943,058 to Carbonetti (1990), a tennis racquet with a fixed grip and moveable frame, utilized the same mechanisms as Melby""s golf club with rotatable handle, and resulted in the same limitations.
U.S. Pat. No. 4,033,593 to Erhart (1977), a tennis racquet with a slip clutch handle, did not permit the user to quickly rotate the handle to desired grip positions and prevent relative rotation between the handle grip and the racquet Rather, the mechanism merely acted as a rotary shock absorber; rotational movement of the handle grip occurred when the playing ball struck on or near the frame at either side of the racquet head.
As with other racquet handle grips, Erhart""s handle grip was also inappropriate for performing a ratcheting effect on screwdrivers.
U.S. Pat. No. 2,712,765 to Knight (1955) shows a rotatable handle grip for hand tools. The user was required to apply longitudinal force against the handle grip with simultaneous resistance against the head of the tool. Such force would overcome the resistance of an internal spring, thereby meshing the teeth of opposing parts; rotational force could then be transmitted from the handle grip to the tool. Clearly, the mechanism could not be applied to racquet handle grips or the like; there would be no way to prevent rotation of the racquet relative to the handle grip during play.
Although a ratcheting effect could be accomplished with this handle grip, there were limitations to its use; i.e. the tool had to encounter resistance when longitudinal force was applied to the handle grip. Also, when used to screw or unscrew long bolts, the user experienced undue effort; prior to each rotation the user was required to overcome the force of the spring. Such a motion repeated many times could be fatiguing as well as time consuming.
Accordingly, the invention has one or more of the objects and advantages of both the rotatable handle grips described above, and the following:
1. To provide a hand powered means of both amplifying the gripping ability of a hand when firmly squeezing, and amplifying the ease in which an item can be rotated when the and is still holding on to it.
2. To provide an interface between a user""s hand and an item embodying the utmost simplicity in design; a device with only one moving part, a handle grip or glove, that stops or allows its own rotation about the shaft of an implement.
3. To provide a rotatable handle grip or band interface embodying the utmost simplicity in operation by:
(a) functioning in almost precisely the same manner as a human hand;
(b) requiring only one almost instantaneous motion effectuated by either firmly squeezing or relaxing had pressure upon the handle grip to respectively stop or allow its rotation about the shaft of an implement;
(c) functioning without pressing levers or longitudinal movements of the handle grip along the shaft of the implement; and,
(d) requiring very little time or effort to learn to use.
4. To provide squeezably stopable rotary handle grips and gloves for many different implements such as tennis racquets, hockey sticks, kayak oars, and screwdrivers, in order to improve the performance of such items.
5. To provide gloves which allow users to easily glide or rotate implements in their hands when using normal gripping pressure, yet provide incredible gripping power when the implements are grasped firmly.
6. To provide a teaching or learning tool for beginning level tennis players which enables them to quickly and easily learn:
(a) what are common grip positions;
(b) what effect different grip positions have on a tennis ball after it is struck, such as its flight path and spin; and,
(c) to switch from one grip position to another.
7. To provide a tool to help and encourage tennis players to remember to change their grip position for different types of shots.
8. To provide rotatable handle grips which are less likely to experience jamming or failure of parts compared to existing rotatable handle grips.
9. To provide rotatable handle grips which remain in an unlocked position when not firmly squeezed, thereby increasing ease and speed of rotational grip position changes.
10. To provide a hand powered hand interface which selectively amplifies torque transfer between a user""s hand and an implement through a squeeze actuated tooth meshing system or frictional brake system.
11. To provide an infinite number of possible rotational grip positions through a squeeze actuated frictional brake system.
12. To provide rotatable handle grips which allow constant hand to handle grip contact without relative movement between the two when rotating the handle grip about the shaft of an implement resulting in:
(a) less time, thought, and effort required to effect rotational grip changes than required with existing handle grips;
(b) a handle grip which is ideally suited to having a contoured surface to ergonometrically fit and position a user""s hand;
(c) greater control over the implement than with a stationary handle grip; and,
(d) less rubbing and chaffing of the ski of the hand than occurs when using a stationary handle grip, especially one with a tacky or high friction surface.
13. To provide squeezably stopable rotary handle grips with contoured surfaces to increase the area of hand to handle grip contact and provide physical barriers to hand and finger movement, resulting in:
(a) greater comfort and control in wielding and maneuvering an implement;
(b) a reduction in the incidence of hand slippage and blisters;
(c) a reduction in hand fatiguexe2x80x94a user can wield an implement while grasping the handle grip very loosely;
(d) greater ease in rotating the handle grip about the shaft of an implement because firm gripping pressure is not needed, thereby helping to prevent accidental, unwanted, squeeze actuated rotation stoppage of the handle grip;
(e) a reduction in the severity of physical trauma to a user""s hands and joints because impact forces are distributed over a greater hand area than with conventional handle grips; and,
(f) greater transmission of torque with minimal squeezing effort whereby,
a tennis player can better resist twisting of a racquet in his hand when a tennis ball strikes the racquet head off center or on its frame, and
a screwdriver or similar rotary hand tool operates more efficiently, not relying solely on the user""s grip strength to twist a screw.
14. To provide a squeezably stopable rotary handle grip for a racquet with ergonometrically contoured surfaces which:
(a) eliminates the need for instruction on how to best grasp the handle grip by positioning a player""s hand in precisely the same optimal hand gripping position every time the racquet is used;
(b) allows the racquet to function as a more natural and effective extension of a user""s arm;
(c) permits a user to produce greater gripping pressure from each finger than when grasping a conventional racquet; and,
(d) improves a user s consistency of play by allowing greater control of the racquet when striking a ball very hard.
15. To provide adjustable relative rotational grip position indicators to improve the accuracy, versatility and practicability of rotatable handle grips for implements such as tennis racquets by:
(a) enabling a user to tactually sense different grip positions, especially the volley position for tennis racquets; and,
(b) allowing a user to select from an infinite number of positions and accurately locate a desired position during play.
16. To provide an end-stop system for a rotatable handle grip on an item such as a tennis racquet which:
(a) restricts the range of relative rotation between the handle grip and the implement:
(b) allows a player to set extreme forehand and extreme backhand rotational grip positions;
(c) can be steplessly adjusted and set to a player""s specifications before, during or after use of the racquet; and,
(d) improves a player""s consistency and response time by providing the predominant grip positions for ground stroke, extreme forehand and backhand positions, very quickly, accurately and easilyxe2x80x94obtaining the same positions every time the racquet is rotated relative to the handle grip clockwise or counterclockwise as far as it will go.
17. To provide rotatable handle grips which can be easily, comfortably and effectively employed by players who grasp a handle grip with two hands when changing rotational grip positions.
18. To provide rotatable handle grips, for implements such as tennis racquets, which have superior shock absorbing and vibration dampening characteristics to previous rotatable handle grips because:
(a) there are fewer moving parts to vibrate against each other;
(b) elements of the handle grips in contact with the racquet shaft fit snugly around the shaft exerting a constant but slight pressure so as to not vibrate against the shaft;
(c) the handle grip comprises shock absorbing materials of different densities, thicknesses and flexibilities which dampen vibration synergistically; and,
(d) shock and trauma normally transmitted to a player""s hand when a ball strikes the racquet head off center or on its frame, can be significantly reduced if the player grasps the handle grip less firmly than usual to allow the racquet head to rotate on impactxe2x80x94control of the racquet is maintained since the grip does not slide out of the user""s hand (although not desirable for normal play, this technique can be used by individuals concerned with joint injuries).
19. To provide rotatable handle grips which are lightweight and do not adversely affect the weight distribution and balance of implements.
20. To provide modular snap-on/off handle grips which:
(a) can be made in a wide variety of sizes, shapes, colors, materials and textures;
(b) can be quickly and easily replaced when worn out, thereby eliminating the need for grip wrapping tapes which are time consuming and bothersome to apply.
21. To provide rotatable handle grips which are simple and inexpensive to manufacture.
22. To provide rotatable handle grips for screwdrivers and other rotary hand tools which can produce a ratcheting effect, allowing a user to instantly switch between clockwise and counterclockwise directions without moving or depressing any buttons, tabs or levers, and has fewer parts than existing ratcheting tools.
Further objects and advantages of the invention will become apparent from a consideration of the drawings and ensuing descriptions of them.